Coal isn't the problem - how we use it is. The solution lies in cleaner technologies and better utilization.

I don't do drugs. I am drugs.

Education is the most powerful weapon which you can use to change the world.

The future is always changing, but the past is always the same.

从n对观测值的样本中获得的相关系数的可能误差是sqrt((1-r²)/(n-2))。